Australia used artificial tree hollows to replace vital wildlife homes lost to bushfires; new 3D-printed and drilled habitats could give threatened species a place to shelter

When huge areas of Australian habitat were destroyed by catastrophic bushfires, the loss was not simply measured in burnt trees. For animals that depended on natural hollows, the destruction meant losing the places where they sheltered and bred. Natural tree hollows can take decades to develop. Some of the information supplied for this story puts that wait at up to 70 years, while the Charles Sturt University research notes that natural hollows can take 80 to 100 years to form, as per a report by Charles Sturt University. That left conservationists facing an obvious problem: how do you replace wildlife homes that nature takes generations to create?

Researchers and conservationists in Australia have been testing two strikingly different answers. One involves 3D printing insulated artificial hollows from recycled plastic. The other uses a specially designed drilling technique to create hollows directly inside living trees.

Both approaches are aimed at the same urgent problem, replacing shelter lost after the 2019-20 bushfires and helping hollow-dependent wildlife find somewhere to live.

Why are tree hollows so important?

The loss of natural hollows matters because they provide shelter and breeding spaces for a large range of Australian wildlife.

Matt Stephens, inventor of the Hollowhog technique and a Transport for NSW environment officer, said 15 per cent of Australia’s wildlife, including 300 species of birds, reptiles and mammals, relied on hollows for shelter.

The hollow’s small entrance is part of what makes it useful. As Stephens explained, “Animals prefer them because of their small entrances, which allow them to tightly squeeze through and avoid threats from larger predators.”

The 2019-20 bushfires made the shortage more urgent. Catastrophic fires destroyed more than 5.5 million hectares of wildlife habitat, leaving millions of animals that relied on tree hollows for shelter and breeding displaced and vulnerable to predators.

At the same time, natural hollows could not simply be replaced overnight.

How are scientists creating artificial wildlife homes?

At Charles Sturt University, researchers from the Institute for Land, Water and Society in Albury-Wodonga and Bathurst developed an artificial nesting hollow using 3D printing technology.

Their 3D-printed plastic hollows were designed to closely mimic the thermal properties, longevity and internal dimensions of natural tree hollows. The design uses double-walled insulation, helping regulate the temperature inside.

Mr Mick Callan, one of Professor David Watson’s research students, tested different construction methods in laboratories and in the field.

“What sets our 3D printed hollows apart from the traditional wooden nest boxes – which have been around for the last 3,000 years – is that they are able to better control the internal temperature,” Mr Callan said.

“This means the nest is much better insulated and provides a more comfortable home for the animals.”

The researchers also expect the artificial hollows to have a lifespan comparable to natural hollows, potentially making them considerably longer-lasting than timber nest boxes, which typically last eight to 10 years.

The project received a $10,000 CSU Green sustainability research grant, while commercial production using 100 per cent recycled plastics is due to begin. A design patent has also been granted, and the hollows are expected to be commercially available through Habitech Pty LtdCharles Sturt University

Did threatened animals actually use the new hollows?

This was one of the most important questions facing the Charles Sturt University researchers. Professor Watson said common Australian wildlife species readily accept artificial nest boxes, but there had been little evidence showing that many threatened species would use them.

The study specifically targeted red-rumped parrots. “Our study targeted red-rumped parrots (pictured) and found these species successfully adopted our 3D nest hollows.”

That finding gave the researchers evidence that their artificial structures could attract a species they were specifically trying to help.

Professor Watson described the development as potentially the first real revolution in nest box design in 3,000 years, particularly at a time when natural hollows have become extremely scarce across areas affected by habitat loss and bushfires.

The problem is not limited to birds. The design is intended for hollow-dependent wildlife ranging from very small birds such as pardalotes to larger species including owls and ducks.

Can living trees be given hollows faster?

The Hollowhog project takes a different approach.

Rather than creating a separate nest box, Stephens developed a drilling technique designed to speed up the formation of hollows within living trees.

Before the Hollowhog, hollow carving involved a chainsaw and removal of a large section of the tree’s outer layer. Stephens said his technique instead requires drilling a small, finger-sized hole into the living material using a specially designed drill head.

The method allows the rest of the tree structure to remain intact while some deadwood is removed from the centre.

“This technology allows us to keep the rest of the tree's structure intact and carefully enter and remove some of the deadwood in the centre of the tree,” he said.

Stephens described the concept simply: “We are bringing forward evolution here.”

At Pillar Valley on the North Coast, landowner Vaughan Kirky had already seen animals seeking refuge after the fires. His property now has 80 hollows created using the technique.

"Tree hollows are not affected by extreme temperatures and are a lot less obtrusive," Mr Kirky said.

"As the tree grows and matures, then so those hollows will actually mature with the trees and they will become even more like a natural habitat."

Transport for NSW had installed more than 800 hollows in bushfire-affected areas under a pilot habitat replacement project. Another 600 hollows had also been commissioned as interest in the technique grew.

The shelters were already attracting wildlife. Transport for NSW senior environment and sustainability officer Kate Dallimore said lorikeets, bush rats and antechinus had taken up the hollows.

"Within 20 minutes of installing a hollow, a tree creeper flew around and inspected the hollow."

For Stephens, the ambition extends far beyond the initial installations. He hopes the technique can eventually be used across Australia and internationally.

"My hope is that this technique can be used not just in New South Wales but across Australia and internationally," he said.

"I call it the one-million-hollow project, where I aim to make a difference to conservation activities and help house displaced animals."

The two approaches show how conservationists are responding to a problem that nature cannot solve quickly. One creates insulated artificial hollows from recycled plastic, while the other accelerates hollow formation inside living trees.

After the destruction caused by the Black Summer bushfires, the challenge is no longer simply protecting wildlife habitat. It is finding ways to recreate the shelter that disappeared, while natural trees take decades to provide it again.

FAQs

Why do Australian animals need artificial hollows?
Natural tree hollows can take decades to form, while many were lost in bushfires.

Are animals using the new hollows?
Yes. Red-rumped parrots, lorikeets, bush rats, antechinus and other wildlife have used or inspected them.